improve devcontainer setup

add renv cache (volume)
restore renv on post create

.devcontainer/Dockerfile

@@ -10,9 +10,6 @@ RUN apt update \
         pandoc \
     && :
 
-# install dev dependencies
-RUN R -q -e 'install.packages("renv")'
-
 WORKDIR /invertr
 
 COPY . .

.devcontainer/devcontainer.json

@@ -7,7 +7,7 @@
 	"context": "..",
 	"runArgs": [
 		"--name",
-		"dev_invertr",
+		"dev_invallor",
 		"--init"
 	],
 	"customizations": {
@@ -18,13 +18,15 @@
 		}
 	},
 	// Features to add to the dev container. More info: https://containers.dev/features.
-	// "features": {},
+	"features": {
+		"ghcr.io/rocker-org/devcontainer-features/renv-cache:latest": {}
+	},
 
 	// Use 'forwardPorts' to make a list of ports inside the container available locally.
 	// "forwardPorts": [],
 
 	// Use 'postCreateCommand' to run commands after the container is created.
-	"postCreateCommand": "R -q -e 'install.packages(\"devtools\")'"
+	"postCreateCommand": ".devcontainer/postcreate.sh"
 
 	// Uncomment to connect as root instead. More info: https://aka.ms/dev-containers-non-root.
 	// "remoteUser": "root"

.devcontainer/postcreate.sh

@@ -0,0 +1,5 @@
+#!/bin/sh
+set -euo pipefail
+
+R -q -e 'install.packages("devtools")'
+R -q -e 'renv::restore()'